Computer and communication technologies continue to advance at a rapid pace. Indeed, computer and communication technologies are involved in many aspects of a person's day. For example, many devices being used today by consumers have a small computer inside of the device. These small computers come in varying sizes and degrees of sophistication. These small computers include everything from one microcontroller to a fully-functional complete computer system. For example, these small computers may be a one-chip computer, such as a microcontroller, a one-board type of computer, such as a controller, a typical desktop computer, such as an IBM-PC compatible, etc.
Computers typically have one or more processors at the heart of the computer. The processor(s) usually are interconnected to different external inputs and outputs and function to manage the particular computer or device. For example, a processor in a thermostat may be connected to buttons used to select the temperature setting, to the furnace or air conditioner to change the temperature, and to temperature sensors to read and display the current temperature on a display.
Many appliances, devices, etc., include one or more small computers. For example, thermostats, furnaces, air conditioning systems, refrigerators, telephones, typewriters, automobiles, vending machines, and many different types of industrial equipment now typically have small computers, or processors, inside of them. Computer software runs the processors of these computers and instructs the processors how to carry out certain tasks. For example, the computer software running on a thermostat may cause an air conditioner to stop running when a particular temperature is reached or may cause a heater to turn on when needed.
These types of small computers that are a part of a device, appliance, tool, etc., are often referred to as embedded devices or embedded systems. (The terms “embedded device” and “embedded system” will be used interchangeably herein.) An embedded system usually refers to computer hardware and software that is part of a larger system. Embedded systems may not have typical input and output devices such as a keyboard, mouse, and/or monitor. Usually, at the heart of each embedded system is one or more processor(s).
A lighting system may incorporate an embedded system. The embedded system may be used to monitor and control the effects of the lighting system. For example, the embedded system may provide controls to dim the brightness of the lights within the lighting system. Alternatively, the embedded system may provide controls to increase the brightness of the lights. The embedded system may provide controls to initiate a specific lighting pattern among the individual lights within the lighting system. Embedded systems may be coupled to individual switches within the lighting system. These embedded systems may instruct the switches to power up or power down individual lights or the entire lighting system. Similarly, embedded systems may be coupled to individual lights within the lighting system. The brightness or power state of each individual light may be controlled by the embedded system.
A security system may also incorporate an embedded system. The embedded system may be used to control the individual security sensors that comprise the security system. For example, the embedded system may provide controls to power up each of the security sensors automatically. Embedded systems may be coupled to each of the individual security sensors. For example, an embedded system may be coupled to a motion sensor. The embedded system may power up the individual motion sensor automatically and provide controls to activate the motion sensor if motion is detected. Activating a motion sensor may include providing instructions to power up an LED located within the motion sensor, output an alarm from the output ports of the motion sensor, and the like. Embedded systems may also be coupled to sensors monitoring a door. The embedded system may provide instructions to the sensor monitoring the door to activate when the door is opened or closed. Similarly, embedded systems may be coupled to sensors monitoring a window. The embedded system may provide instructions to activate the sensor monitoring the window if the window is opened or closed.
Some embedded systems may also be used to control wireless products such as cell phones. The embedded system may provide instructions to power up the LED display of the cell phone. The embedded system may also activate the audio speakers within the cell phone to provide the user with an audio notification relating to the cell phone.
Home appliances may also incorporate an embedded system. Home appliances may include appliances typically used in a conventional kitchen, e.g., stove, refrigerator, microwave, etc. Home appliances may also include appliances that relate to the health and well-being of the user. For example, a massage recliner may incorporate an embedded system. The embedded system may provide instructions to automatically recline the back portion of the chair according to the preferences of the user. The embedded system may also provide instructions to initiate the oscillating components within the chair that cause vibrations within the recliner according to the preferences of the user.
Additional products typically found in homes may also incorporate embedded systems. For example, an embedded system may be used within a toilet to control the level of water used to refill the container tank. Embedded systems may be used within a jetted bathtub to control the outflow of air.
Embedded systems may establish connections to other electronic devices for a variety of reasons. For example, an organization may want to make data about its embedded systems available to certain remote clients. An embedded system may also allow these remote clients to control the behavior of the embedded system. For example, problems found with calibration may be adjustable remotely instead of sending a person to the location of the embedded system. Alternatively, or in addition, the embedded system may allow its behavior to be changed remotely in much the same way it can be changed locally. One example would be locking a door remotely. This kind of remote control is not limited to the functionality available locally, and in many cases may exceed the local capabilities. One example would be a sensor that has no local interface but allows remote control of its behavior.
To communicate with other electronic devices, an embedded system may connect to a computer network. Sometimes it is desirable for an embedded system to send a message to a group of electronic devices that are located in one or more computer networks. Where the recipient group is numerically large in size but small compared to the overall number of devices in the network(s), multicast routing is often used. Multicasting refers to the process of sending a message simultaneously to more than one destination on a network. Multicasting is different from broadcasting in that multicasting means sending to specific groups within a network, whereas broadcasting implies sending to everybody on the network. With multicast technology, the bulk of the data is typically transmitted once from its source through major backbones of the network and is multiplied, or distributed out, at switching points closer to the destinations.
The User Datagram Protocol (UDP) may be used in connection with multicast routing. This is often referred to as UDP multicasting. UDP provides a way for applications to send encapsulated IP datagrams and send them without having to establish a connection.
A problem may arise when an embedded system tries to send a message via UDP multicasting to electronic devices that are located in different networks. Computer networks may be constrained to isolate specific network traffic, and to allow restricted sets of computers to communicate. These constraints, imposed by network devices such as routers and firewalls, purposely limit the use of UDP multicast addressing. If two networks are separated by a networking device that is not configured to route multicast addressing, then it may be difficult for multicast requests that originate on one isolated network to be delivered to computers on another isolated network. Accordingly, what is needed are mechanisms for providing a network bridge for UDP multicast traffic, i.e., for getting multicast packets from one network to another network across networking devices that are not configured to route multicast addressing.